This invention relates to a control apparatus for a hybrid vehicle, which provides an electric motor directly connected to an engine having both driving and power-generating functions, and which executes an automatic start-up/stop control of the engine.
Some motor vehicles are of a type commonly called a hybrid vehicle having an internal combustion engine driven by combustion of fuel and an electric motor (herein described as xe2x80x9cmotorxe2x80x9d) driven by electric energy, wherein the motor is directly connected to the engine and also has a power-generating function. The hybrid vehicle further includes an engine control means for controlling a running state of the engine and motor control means for controlling an operating state of the motor. The engine control means and the motor control means detect respective operating states of the engine and the motor when the vehicle is traveling, and then exchange such detected data regarding the running states. As a result, the respective operating states of the engine and the motor are controlled in association with one another. Such a control system attains a high level of required performance (such as fuel efficiency, lower values of detrimental components in exhaust gases, and power performance). The apparatus includes a main battery which supplies drive electricity to the motor and is charged by recharging power-generation by the motor. A required amount of battery charge must be maintained in order to perform suitable driving power-generation/driving prohibition for the motor. This apparatus administers the battery.
Moreover, there is a hybrid vehicle which has an automatic start-up/stop control means to improve mileage and/or reduce release of effluent gas, by stopping an engine forcibly at an idling state.
One such example of a control apparatus of a hybrid vehicle is disclosed in published Japanese Application Laid-Open No. 10-136508. In the hybrid vehicle of this disclosure an engine usually starts up by cranking a motor. But when a start-up by a motor is impossible, an engine start control means controls start up by cranking the engine with a starter motor. Therefore, when engine start up by cranking of a starter motor is required, the engine start control means functions to assist cranking of the engine.
Incidentally, during operation of automatic start-up/stop control, at a restart-up of an engine and a restart-up in an idle stop, a control apparatus of a traditional hybrid vehicle judges whether an engine is started by electric motor only or starter motor only. But this system must control collectively the engine and the motor. Accordingly, the system is complicated in hardware and software, and becomes expensive.
In order to obviate or minimize the above problem or expense, the present invention provides a control apparatus for a hybrid vehicle having a motor directly connected with an engine mounted on the vehicle. The motor has both driving and power-generating functions. The control means executes automatic start-up/stop control of the engine. The control means starts up the engine using a starter motor by operation of a key and assists start up using the electric motor. During automatic start-up/stop control of the engine, at restarting of the engine when a start-up condition is satisfied, the control means controls to start up the engine using only the electric motor. At restart-up of the engine when a start-up condition is not satisfied, the control means drives the starter motor and the electric motor by outputting an engine activation signal so that the starter motor is assisted by the electric motor.
The engine control means and motor control means operate independently. In particular, in a start-up system, the engine control means operates as master, and the motor control means operates as slave. in this system, the engine and motor are not collectively controlled, and simplification of the system is achieved in both hardware and software. In addition, synchronism of the engine and the motor is achieved, and both certain start-up and restart-up of the engine are gained. Furthermore, quietness at restart-up of the engine is gained. Fundamentally, the electric motor is started by voltage from a main battery when the voltage value exceeds a predetermined voltage. In this system, the electric motor assumes the role of starter motor when an appropriate water temperature and battery voltage are sensed. The arrangement improves the durability of the starter motor. In addition, life of the sub-battery is improved.